1. Technical Field
The invention relates to fiber optical collimators. More particularly, the invention relates to an asymmetric sleeve for the fiber optical collimators and methods for making the asymmetric sleeve.
2. Description of the Prior Art
In most of modern fiber optical components, collimators are often used to collimate light leaving fibers and focus collimated light to fibers or devices. There is a strong need to reduce the sizes of all fiber optical components since smaller sizes can reduce the overall cost and weight of a fiber optical system and can thus increase its portability and reliability. The collimator size often becomes an important issue, even a limiting factor in many cases, for the overall size of a resultant component. For example, for three-port fiber optical circulators, if three collimators need to be used, i.e., each collimator for each port, the lateral dimension thereof is often limited by the space occupied by the side of port 1 and port 3 collimators. In addition to the space issue, the crystals used in such circulators must be big enough to accommodate the big light beam separation created by the port 1 and port 3 collimators separation.
One type of three-port circulators was proposed to include only two collimators so as to reduce the circulator size and associated crystal cost. But those circulators with only two collimators are difficult to align as a result of the more complicated optical paths that are needed to use a single collimator for two ports. Therefore, it is highly desirable to use three collimators and simple traditional circulator optical configurations, and at the same time, still have small physical sizes.
FIG. 1A shows a commonly used collimator 100 comprising a ferrule 102, a rod lens 104 and a cylindrical sleeve, wherein a fiber 108 is encapsulated in the ferrule 102. A perspective view of the collimator 100 is shown in FIG. 1B. The minimum achievable size of a collimator is determined by the outer diameter of the cylindrical sleeve for a given size of the rod lens and ferrule.
In the type of the circulator that includes three collimators as described above, one will have to arrange two collimators next to each other. However, the center to center distance L of the two adjacent collimators cannot be less than D, the outer diameter of the cylindrical sleeve as shown in the FIG. 1C. In real applications, it will be desirable to have such two collimators arranged next to each other while the center to center distance L is less than D.
The present invention, generally speaking, provides a new design of fiber collimators that include an asymmetric sleeve. According to one embodiment of the present invention, the asymmetric sleeve is so shaped that, when arranged next to each other, two collimators with the asymmetric sleeve achieves a lateral distance shorter than the outer diameter of the collimators. One of the advantages or benefits is that the reshaped sleeve of a collimator can make it possible to design smaller optical components without effecting the performance and characteristics thereof. As a result, the sizes of the materials or components such as crystals in circulators and prisms in opto-mechanical switches can be reduced.
One of the objects of the present invention is to provide a new design of optical collimators that, when used in multiple, can be arranged in a reduced dimension.
Other objects, features, and advantages of the present invention will become apparent upon examining the following detailed description of an embodiment thereof, taken in conjunction with the attached drawings.